1. Field of the Invention
The present invention relates to a charged particle beam deflector, and particularly to an improvement of a blanking aperture used on an electron beam deflector, electron beam exposure apparatus, etc., that is capable of collectively drawing patterns using multiple beams or patterned beams.
2. Description of the Related Art
Electron beam exposure techniques used for manufacturing semiconductor integrated circuits must have a pattern drawing accuracy of submicron order. To draw a pattern at this accuracy, it takes a long time if a very fine variable rectangular beam is employed. To shorten the time, various studies have been made to employ a line beam that realizes a plurality of simultaneous shots.
FIG. 6 is a schematic view showing an example of a charged particle beam deflector used for an electron beam exposure apparatus.
A blanking aperture array 1 includes a plurality of apertures 1'a, 1'b, and so on. Each of the apertures has a pair of blanking electrodes for deflecting (turning on and off) a charged particle beam (an electron beam). An electron gun 42 emits an electron beam, which passes through the blanking apertures 1'a, 1'b, and so on, as well as a main deflector 43 and a subdeflector 44, and draws patterns on a wafer 46 placed on a stage 45.
A CPU 47 provides drawing data stored in a memory 48 to a bit map generator 52, which provides a bit map. According to the bit map, a group of blanking generators 53 control the electrodes of the apertures 1'a, 1'b, and so on to turn on and off components of the beam passing through the apertures, respectively.
A sequence controller 54 receives data from an interface 50 and sequentially controls the bit map generator 52, a blanking controller 55, a deflector controller 56, and a stage controller 57. The blanking controller 55 controls the blanking generators 53, and the deflection controller 56 controls the main deflector 43 and subdeflector 44. The stage controller 57 controls the position of the stage 45 with a step motor 60.
FIGS. 7(A) and 7(B) are views showing an example of a conventional blanking aperture, in which FIG. 7(A) is a top view and FIG. 7(B) a sectional view along a line X--X of FIG. 7(A).
A conductive or semiconductive substrate 2 has an opening of, for example, a square shape. Insulation films 3 are formed on inner walls S and S' of the opening, and deflecting electrodes 10 and 11 are formed on the insulation films 3. Lead metalized pattern 14 and 15 are provided for the deflecting electrodes 10 and 11, respectively. Each of the blanking apertures 1'a, 1'b, and so on of FIG. 6 is formed in this way.
This arrangement is insufficient, even with a predetermined voltage applied to the deflecting electrodes 10 and 11, to deflect and completely move a beam out of an aperture corresponding position on the wafer 46. Namely, the beam may remain on the wafer 46 to blur a pattern drawn on the wafer 46. This problem may be solved by increasing the voltage applied to the deflecting electrodes 10 and 11. This, however, increases costs.
FIGS. 8(A) and 8(B) are views showing an example of a conventional blanking aperture for generating a patterned beam, in which FIG. 8(A) is a top view and FIG. 8(B) a sectional view along a ling X--X of FIG. 8(A).
This blanking aperture is used for repeatedly drawing a relatively large pattern on a wafer. The blanking aperture is made from an aperture board 200 having an aperture 101 for providing a patterned beam, and a deflecting board 201 having substantially the same arrangement as that of the blanking aperture shown in FIGS. 7(A) and 7(B).
In FIGS. 7(A) and 7(B), opposing inner walls L and L' where the deflecting electrodes 10 and 11 do not exist are at a ground potential level. Accordingly, lines H of electric force from one of the deflecting electrodes (for example, 11) are curved to enter the inner walls L and L', thereby reduce the quantity of lines of electric force reaching the electrode 10. As a result, a uniform electric field is not provided. To compensate for this insufficient electric field formed inside the aperture, the deflection voltage must be increased.
In FIGS. 8(A) and 8(B), the aperture board 200 and deflecting board 201 for generating a patterned beam must be separately prepared and combined after axially aligning them. This deteriorates operability.
In recent years, many apertures are prepared and collectively controlled to simultaneously expose many positions of a wafer to expedite the exposing process. For this purpose, a number of blanking apertures are densely arranged (1'a, 1'b, and so on in FIG. 6), sometimes in a plurality of lines. In these cases, the distance between adjacent apertures is very small, so that electric fields generated in the adjacent apertures may interfere with each other to inaccurately deflect components of a beam passing through the apertures.